We report results of a combined experimental and computational model study on the interaction of the battery-relevant ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMP-TFSI) with a Mg thin film model electrode grown on a Ru(0001) substrate, which aims at a fundamental understanding of the solid electrolyte interphase formation at the electrode–electrolyte interface in postlithium batteries. Scanning tunneling microscopy, x-ray photoelectron spectroscopy (XPS), and ultraviolet photoelectron spectroscopy were employed for the characterization of the Mg thin film model electrode, revealing oxygen-free and atomically flat Mg films. Room temperature XPS measurements after vapor deposition of a (sub)monolayer of BMP-TFSI on the Mg film revealed the formation of a “contact layer” on Mg(0001), created by the reactive decomposition of the IL. In agreement with computationally determined core level binding energies of stable reaction products (dispersion corrected density functional theory calculations), we identified mainly inorganic MgF2-, MgO-, and MgS-like surface compounds, but also other more complex (Mg2+-free) F-, O-, and/or S-containing “TFSI-like” and carbon-containing adsorbed species. The deposition of higher IL amounts (up to 6 monolayers) results in the overgrowth of the direct “contact layer” by molecularly adsorbed BMP-TFSI. Heating of the adsorbate covered surface to around 470 K leads to desorption of multilayer BMP-TFSI and the partial desorption and transformation of adsorbed (Mg2+-free) “TFSI-like” decomposition products on the Mg substrate into MgF2-, MgO-, and MgS species or the respective adsorbed Fad, Oad, and Sad species.
We report uniform liquid crystal (LC) alignment on a polyacrylamide (PAM) film via ion beam (IB) treatment. The IB incidence angle is adjusted from 15° to 75°. Physicochemical modifications caused by the IB process are investigated by atomic force microscopy and x-ray photoelectron spectroscopy. Low IB incidence results in biased and bumpy surfaces, whereas high IB incidence forms isotropic and smooth surfaces; both of these are unsuitable for uniform LC alignment. The 45° IB incidence induces anisotropic surface chemical reformations, and these modifications induce van der Waals forces between the LCs and modified PAM, thereby leading to uniform LC alignment. The LC alignment state is verified by polarized optical microscopy and pretilt angle. The electro-optical characteristic of the modified PAM showed excellent switching performance in twisted-nematic LC system. Thus, the IB-treated PAM film is a good candidate for LC alignment layers and suitable for LC device applications.
In doped manganites, a substantial tuning of the magnetic and electrical transport properties can be realized by engineering the concentration of oxygen vacancies. To date, most oxygen-deficient La1−xSrxMnO3−δ (0 ≤ x ≤ 1) films are synthesized by after-growth treatments. However, the direct growth of La1−xSrxMnO3−δ films remains challenging due to the metastability of this material. Here, we report the epitaxial growth of high quality single crystalline La0.67Sr0.33MnO3−δ films with an extremely large out-of-plane lattice parameter of 4.26 Å by reactive oxide molecular beam epitaxy. To stabilize this metastable phase, Sr3Al2O6 buffer layers are used to block the oxygen diffusion from the SrTiO3 substrate to the film during the growth process. This work provides an efficient way to obtain metastable La0.67Sr0.33MnO3−δ films.
Thin films of silver were deposited on nonalkali glass substrates at substrate temperatures ranging from room temperature (28 °C) to 150, 200, 300, 400, and 500 °C at discharge pressures of 0.40, 1.20, and 2.00 Pa using direct current magnetron sputtering. On the basis of the measured cross-sectional and surface morphologies, crystallographic structures, and film properties, I discuss the dependence of the film structure and properties on the substrate temperature. The x-ray diffraction measurements showed that the <111> orientation was preferred for all deposition conditions. Scanning electron microscope observations revealed a microstructure of convex-shaped fine grains for a substrate at room temperature, while laterally growing, mound-shaped grains with flat-topped surfaces appeared at substrate temperatures of 400 and 500 °C. Atomic force microscopy also showed an increase in the lateral size and height of the mound-shaped structures with increasing substrate temperature. The lateral grain size evaluated from the areal particle density obtained from atomic force microscopy increased significantly with increasing substrate temperature, reaching 600–800 nm at a substrate temperature of 500 °C. The film stress also changed from compressive to tensile with increasing substrate temperature. The relative density, defined as the ratio of the deposited amount-of-substance to the physical-thickness, decreased significantly with increasing substrate temperature and, at a substrate temperature of 500 °C, was approximately 0.6 times as large as that obtained for thin films deposited at room temperature. The high surface diffusivity of the Ag adatoms induces the growth of laterally growing, mound-shaped grains. Besides, the energy accumulated in the thin films during sputter deposition induces the void formation to increase the efficiency of energy release in the form of heat.
